Try a couple of things...
1. Try connecting to someone else's wifi or a free wifi hotspot to see if there are problems connecting to a different source. If you can't connect to anyone else wifi then it could well be the card.
2. Open System Preferences then Network, click on your airport card, click Advanced, in the network list click your network then click the minus symbol to make it forget the network connection, next logout, log back in and re-connect to your wifi, see if that clears it.
3. You could also try repairing your disk and repairing disk permissions, to repair disk boot your MBP into your install disk, at the top menu click utilities then click disk utility click your HDD then click repair disk, once this has completed click on repair disk permissions.
Hope one of these helps/ works.
- Simon